Observation of microstructure deformation and damage in nuclear graphite

A full field strain mapping technique is employed to obtain in situ, load resolved, strain fields from the surface of disc compression and tensile test specimens of Gilsocarbon IM1-24 nuclear graphite. Analysis of these fields is used to show the development of the distribution of localised deformation, which can be linked to the microstructure and damage processes. Cracks are observed to nucleate at porosity, and to propagate by coalescence. The stability of the cracks depends on the stress state. Such observations may be used to verify microstructure-based models for graphite failure.